Various electric systems for vehicles are proposed for instance in US 2004/0164616A1 (JP 2004-260908A).
Turbo generators for performing electric power generation by utilizing excess of exhaust energy used by a turbocharger are proposed in JP 2000-45817A. A turbo generator is configured to include a generator turbine disposed parallel with a turbocharger and an alternating current (AC) generator for performing power generation in direct connection with the generator turbine. The generator turbine is rotated by absorbing exhaust gas energy (exhaust energy) flowing through a waste gate valve that opens when the gas pressure of the turbocharger reaches a predetermined value. With the rotation, the AC generator directly coupled to the generator turbine performs electric power generation. However, occurrence of such a high engine output as to cause exhaust flow to the waste gage valve is not so frequent that the effect of utilizing the exhaust energy is not exhibited to satisfaction.